Conditioning of textile fabrics

ABSTRACT

Moisture content of a textile fabric is raised by passing moist air through the fabric. Total moisture content of the air is gaseous, i.e., air is not completely saturated. Fabric is supported during treatment by a movable air-permeable surface, e.g., a drum or conveyor belt, and a fan forces the moist air through the fabric after the air passes through a humidifier.

United States Patent [72] Inventors JohnAlbertMedley Leeds; Thomas Gerald Cawthray, Ilkley, both of, England [2]] Appl. No. 785,669

[22] Filed Dec. 20, 1968 [45] Patented Sept. 14, 1971 [73] Assignee Wool Industries Research Association Leeds, England [32] Priority Dec. 23, 1967 [33] Great Britain [54] CONDITIONING 0F TEXTILE FABRICS 6 Claims, 4 Drawing Figs.

[52] US. Cl 34/23,

[51] Int. Cl F26b 3/00 [50] Field of Search 165/19, 20, 21, 60, 37, 23

[56] References Cited UNITED STATES PATENTS 3,088,224 5/1963 Cohn et al. 34/37 3,263,737 5/1966 Brummendorf 165/20 Primary ExaminerCharles Sukalo AttorneyBreitenfeld & Levine ABSTRACT: Moisture content of a textile fabric is raised by passing moist air through the fabric. Total moisture content of the air is gaseous, i.e., air is not completely saturated. Fabric is supported during treatment by a movable air-permeable surface, e.g., a drum or conveyor belt, and a fan forces the moist air through the fabric after the air passes through a humidifier.

PATENTEU SEPJ 4:911 3604.124 sum 3 OF 3 CONDITIONING F TEXTILE FABRICS The invention concerns the treatment of textile fabric of the kind (hereinafter termed of the kind referred to) consisting of or containing hydrophilic or hygroscopic material, the treatment being designed to raise the moisture content of the fabric from a lower value to a uniform known value, this process being known generally as conditioning.

During certain kind of textile processing such as cropping, decatizing, raising or embossing for example, it is desirable to have the fabric at a uniform known moisture content. Similarly after processing, fabric for sale may be advantageously at a uniform specified moisture content, such then being sold in sealed moisturetight packages.

Fabric is frequently drier than the optimum moisture content for a particular process after a previous process such as thermal drying or some other process involving heating of the fabric.

Various methods of conditioning textile fabric are known. In one method liquid water is sprayed directly on to the fabric. In another method a mist of liquid water is formed in air and this mist-laden air is passed through the fabric with consequent deposition of water on the fabric but in this case the air is only a transport medium and the major part of the water has not left the liquid phase. In both these methods the uniformity of moisture content is not good, since the liquid is deposited predominently on the outside of the yarn and on one side of the cloth. Differential wetting effects may occur. Although most of the moisture subsequently transfers to the interior of all the hygroscopic fibers an even distribution of moisture content takes many hours to become established. Additionally the absorption of the liquid water into the fiber can cause a temperature rise in the fabric which may be detrimental. Finally, it is difficult to control the percentage of water added.

Yet another known method of conditioning has been to allow the fabric to stand in an air conditioned room or chamber for a long period of time in which case the moisture content of the fabric tends to reach a level in equilibrium with the air conditions. A refinement is to pass the fabric in festoons through an air conditioned or humidified chamber with forced air circulation such that the air impinges on the outer surface of the fabric but does not penetrate significantly through the fabric. However, these methods are slow, require large plants and are inconvenient for direct coupling to other machines.

It is an object of the invention to overcome at least to some extent the disadvantages of the known methods aforesaid for conditioning textile fabric.

The present invention is based on an appreciation of the possibility of making use of the property of textile fabric, of the kind referred to, rapidly to approach equilibrium with air containing water vapor which is entirely gaseous if such air is compelled to flow in sufiicient quantity through the fabric, and on an appreciation that the moisture content of the fabric cannot exceed an equilibrium value corresponding to the vapor pressure of gaseous water vapor in such air. Furthermore the absorption of this gaseous water vapor results in liberation of latent heat of condensation of water vapor and heat of absorption of liquid water, such heat being removed by the air stream to give some control of the fabric temperature.

According to the present invention a method of conditioning textile fabric of the kind referred to comprises the steps of providing a supply of air, closely controlling the temperature and humidity of the air such that its total moisture content is gaseous, and forcing a stream of such air to pass through the fabric, whereby the moisture content of the fabric is relatively rapidly increased to a desired level. In this way the moisture is within the fibers of the fabric and not merely applied to one side of the fabric.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which:

FIG. I is a side elevation of one form of apparatus for carrying out the invention;

FIG. 2 is a plan view of the apparatus shown in FIG. I;

FIG. 3 is a side elevation of an alternative form of apparatus; and

FIG. 4 is a similar view of a still further form of apparatus.

In the examples to be described the textile fabric comprises a length of woven woolen cloth.

Referring to FIGS. 1 and 2, the cloth 5 is progressed continuously over and around a plurality of perforated drums 6,

the cloth being supplied to and collected from each drum by guide rollers 7 in such a manner that the cloth covers substantially the whole periphery of each drum. The movement of cloth through the machine may be arranged either by an external tractive force such as tension from a following processing machine or by a drive 8 to one or more of the drums, or by any other suitable method.

Air is humidified to controlled conditions by evaporation of water from a large surface area or by some other humidifying device such as mixing steam with the air. This is shown as the humidifying device 9 of FIGS. 1 and 2. It is important that the total moisture content of the air is gaseous such that the air is never completely saturated with water vapor and there are no liquid droplets. This is achieved by temperature control by means of heating heat exchange surfaces at 10 or 11 or by means of cooling heat exchange surface 11. The drums are disposed in an enclosed chamber 12 and a fan I3 draws air under suction from the interior of the drums and circulates the air through the air conditioning device back to the chamber.

The method of recirculation of air enables the heat liberated during the conditioning process to be employed to evaporate more water in the humidifying device.

In an alternative embodiment the machine comprises a single perforated drum 18 inches in diameter with traction for the cloth being provided by a separate roller system. Cloth 62 inches wide and with a dry weight of 7 ounce/square yard can be conditioned from 6% regain to 14 Pkregain at an operating speed of l yard/minute using an air velocity of 19 feet/minute through the cloth, the air being at 32 centigrade and 76 percent relative humidity. The maximum regain which could have been reached would have been 17 percent at a very low cloth speed through the machine. To scale up this machine to a throughput of 15 yards/minute under the same process conditions would involve increasing the length of fabric within the machine through which air is forced at any one instant of time by a factor 15, for example by adding a further 14 drums. The volumetric throughput of air to the machine would also be increased 15 times, but no other conditions need be altered.

In the embodiment shown in FIG. 3, the air is supplied by means of a fan 13, a humidity control device 9 and temperature control devices 10 and 11 under pressure to the interior of perforated drums 6 from where the air emerges through the cloth 5 into an enclosing chamber 12. The air is recirculated through the humidity control device. If the chamber is omitted the fan may draw on air external to the machine.

The FIG. 4 embodiment utilizes a conveyor 15 which is permeable to air, the cloth 5 being supported by the conveyor. Methods of supplying air under controlled conditions are as in the previous examples.

The advantage of these embodiments is rapid achievement of uniformity of moisture content in the cloth and an approach to a final moisture content in equilibrium with the air conditions. Mathematical relationships may be set up which adequately describe the conditioning process and the relationships which exist between the cloth weight, the cloth moisture content, the cloth temperature, the humidity and temperature of the air supplied, the air velocity through the cloth and the matter and heat exchange characteristics between the cloth and the air stream during the approach to equilibrium.

The final moisture content of the cloth may be controlled in several ways, some examples of which are outlined below.

In one method the air may be conditioned to predetermined fixed conditions of temperature and humidity and passed in sufficient quantity through the cloth to ensure that the latter approaches equilibrium with the air. This method is particularly suitable when there are large differences of initial moisture content across the width of the cloth. For example, if the air has a temperature in the range of 1C. to 99 C. and a relative humidity in the range 2 percent to 95 percent, and preferably 40 percent to 95 percent, and is passed in sufficient quantity through woolen cloth, the moisture content of the cloth can be controlled to lie anywhere in the range 7 percent to 28 percent or thereabouts. The required air velocity is subject to the relationship:

V 0.3 WS/L feet/minute where V superficial air velocity through the fabric (feetlminute) W= weight of hydrophilic or hygroscopic fabric portion (ounces/yard) S speed of fabric through machine (yardsyminute) L length of fabric in machine through which air is forced at any one instant of time (yards) The maximum permitted velocity must be such as will not cause permanent distortion of the fabric.

Another method of control is to utilize lesser volumes of air of a higher relative humidity than the desired equilibrium value and to employ a feedback control to adjust continuously either the operating speed of the machine or the velocity of air through the fabric to ensure that the cloth leaves the machine at the required moisture content.

Another method of control is to use a feed forward control system whereby the moisture content of the cloth entering the machine is measured and this signal is used to adjust either the velocity of air through the cloth, the humidity of the air passing through the cloth, or the operating speed of the machine.

It will be appreciated that it is not intended to limit the invention to these examples only, many variations being possible without departing from the scope thereof.

We claim:

l. A method of conditioning moving textile fabric consisting at least in part of hydrophilic or hygroscopic material, comprising the steps of providing a supply of air, closely controlling the temperature and humidity of the air such that its total moisture content is gaseous, and forcing a stream of such air to pass through the fabric, the velocity of the air stream being defined by the relationship:

V (0.3WS/L feet/minute where W is the weight of the hydrophilic or hygroscopic portion of the fabric in ounces/yard,

S is the speed of movement of the fabric in yards/minute,

and

L is the length of fabric through which the air is forced at any one instant of time in yards.

2. A method according to claim 1, wherein the air contains only gaseous water vapor and has a temperature in the range 1 C. to 99 C. and a relative humidity in the range 2 percent to percent.

3. A method according to claim 2, wherein the stream of air is passed through the fabric for a length of time sufficient to permit the moisture content of the fabric to approach equilibrium with the moisture content of the air.

4. A method according to claim 2, wherein a feedback control is employed to adjust continuously at least one of the process variables to maintain the conditioned fabric at the required uniform moisture content.

5. A method according to claim 2, wherein at least one of the process variables are controlled in accordance with the moisture content of the unconditioned fabric to maintain the conditioned fabric at the required uniform moisture content.

6. A method according to claim 2 wherein the heat liberated during the conditioning process is utilized at least in part to assist in the evaporation of further water as vapor into a recirculated airstream. 

2. A method according to claim 1, wherein the air contains only gaseous water vapor and has a temperature in the range 1* C. to 99* C. and a relative humidity in the range 2 percent to 95 percent.
 3. A method according to claim 2, wherein the stream of air is passed through the fabric for a length of time sufficient to permit the moisture content of the fabric to approach equilibrium with the moisture content of the air.
 4. A method according to claim 2, wherein a feedback control is employed to adjust continuously at least one of the process variables to maintain the conditioned fabric at the required uniform moisture content.
 5. A method according to claim 2, wherein at least one of the process variables are controlled in accordance with the moisture content of the unconditioned fabric to maintain the conditioned fabric at the required uniform moisture content.
 6. A method according to claim 2 wherein the heat liberated during the conditioning process is utilized at least in part to assist in the evaporation of further water as vapor into a recirculated airstream. 